Showing papers by "Vito Latora published in 2007"
TL;DR: In this article, a new class of measures of structural centrality for networks is introduced, called delta centralities, which is based on the concept of efficient propagation of information over the network.
Abstract: We introduce delta centralities, a new class of measures of structural centrality for networks. In particular, we focus on a measure in this class, the information centrality C I , which is based on the concept of efficient propagation of information over the network. C I is defined for both valued and non-valued graphs, and applies to groups as well as individuals. The measure is illustrated and compared with respect to the standard centrality measures by using a classic network data set. The statistical distribution of information centrality is investigated by considering large computer generated graphs and two networks from the real world.
374 citations
TL;DR: Based on cluster desynchronization properties of phase oscillators, an efficient method is introduced for the detection and identification of modules in complex networks with a high level of precision.
Abstract: Based on cluster desynchronization properties of phase oscillators, we introduce an efficient method for the detection and identification of modules in complex networks. The performance of the algorithm is tested on computer generated and real-world networks whose modular structure is already known or has been studied by means of other methods. The algorithm attains a high level of precision, especially when the modular units are very mixed and hardly detectable by the other methods, with a computational effort O(KN) on a generic graph with N nodes and K links.
240 citations
TL;DR: The findings support the hypothesis that a self-organized criticality mechanism with long-range interactions is at the origin of seismic events and indicate that it is not possible to predict the magnitude of the next earthquake knowing those of the previous ones.
Abstract: We perform an analysis on the dissipative Olami-Feder-Christensen model on a small world topology considering avalanche size differences. We show that when criticality appears, the probability density functions (PDFs) for the avalanche size differences at different times have fat tails with a q-Gaussian shape. This behavior does not depend on the time interval adopted and is found also when considering energy differences between real earthquakes. Such a result can be analytically understood if the sizes (released energies) of the avalanches (earthquakes) have no correlations. Our findings support the hypothesis that a self-organized criticality mechanism with long-range interactions is at the origin of seismic events and indicate that it is not possible to predict the magnitude of the next earthquake knowing those of the previous ones.
135 citations
TL;DR: A novel approach to quantify the vulnerability of a complex network, i.e., the capacity of a graph to maintain its functional performance under random damages or malicious attacks, that makes use of combined powers of the links' betweenness.
Abstract: We present a novel approach to quantify the vulnerability of a complex network, i.e., the capacity of a graph to maintain its functional performance under random damages or malicious attacks. The proposed measure represents a multiscale evaluation of vulnerability, and makes use of combined powers of the links’ betweenness. We show that the proposed approach is able to properly describe some cases for which earlier measures of vulnerability fail. The relevant applications of our method for technological network design are outlined.
74 citations
TL;DR: In this paper, a way to simulate the basic interactions between two individuals with different opinions, in the context of strategic game theory, is proposed, where various games are considered, which produce different kinds of opinion formation dynamics.
Abstract: A way to simulate the basic interactions between two individuals with different opinions, in the context of strategic game theory, is proposed. Various games are considered, which produce different kinds of opinion formation dynamics. First, by assuming that all individuals (players) are equals, we obtain the bounded confidence model of continuous opinion dynamics proposed by Deffuant et al. In such a model a tolerance threshold is defined, such that individuals with difference in opinion larger than the threshold can not interact. Then, we consider that the individuals have different inclinations to change opinion and different abilities in convincing the others. In this way, we obtain the so-called "Stubborn individuals and Orators" (SO) model, a generalization of the Deffuant et al. model, in which the threshold tolerance is different for every couple of individuals. We explore, by numerical simulations, the dynamics of the SO model, and we propose further generalizations that can be implemented.
64 citations
TL;DR: An analytic method is proposed to measure the stability of the synchronous state (SSS) the subgraph displays and it is shown that, for undirected graphs, the SSS is correlated with the relative abundance, while in directed graphs the correlation exists only for some specific motifs.
Abstract: We address the problem of understanding the variable abundance of 3-node and 4-node subgraphs (motifs) in complex networks from a dynamical point of view. As a criterion in the determination of the functional significance of a n-node subgraph, we propose an analytic method to measure the stability of the synchronous state (SSS) the subgraph displays. We show that, for undirected graphs, the SSS is correlated with the relative abundance, while in directed graphs the correlation exists only for some specific motifs.
52 citations
TL;DR: In this paper, it was shown that Probability Density Functions (PDFs) for the avalanche size differences at different times have fat tails with a q-Gaussian shape, and that this behavior does not depend on the time interval adopted and it is also found when considering energy differences between real earthquakes.
Abstract: We discuss recent results on a new analysis regarding models showing Self-Organized Criticality (SOC), and in particular on the OFC one. We show that Probability Density Functions (PDFs) for the avalanche size differences at different times have fat tails with a q-Gaussian shape. This behavior does not depend on the time interval adopted and it is also found when considering energy differences between real earthquakes.
35 citations
TL;DR: A fully nonhierarchical network growing mechanism, that furthermore does not impose explicit preferential attachment rules, that produces a graph featuring power-law degree and clustering distributions, and manifesting slightly disassortative degree-degree correlations.
Abstract: We introduce a fully nonhierarchical network growing mechanism, that furthermore does not impose explicit preferential attachment rules. The growing procedure produces a graph featuring power-law degree and clustering distributions, and manifesting slightly disassortative degree-degree correlations. The rigorous rate equations for the evolution of the degree distribution and for the conditional degree-degree probability are derived.
20 citations
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TL;DR: In this paper, the authors investigated the case of Bologna, northern Italy, about how much higher street centrality statistically "determines" a higher presence of activities (shops and services).
Abstract: In previous research we defined a methodology for mapping centrality in urban networks. Such methodology, named Multiple Centrality Assessment (MCA), makes it possible to ascertain how each street is structurally central in a city according to several different notions of centrality, as well as different scales of "being central". In this study we investigate the case of Bologna, northern Italy, about how much higher street centrality statistically "determines" a higher presence of activities (shops and services). Our work develops a methodology, based on a kernel density evaluation, that enhances standard tools available in Geographic Information System (GIS) environment in order to support: 1) the study of how centrality and activities are distributed; 2) linear and non-linear statistical correlation analysis between centrality and activities, hereby named Kernel Density Correlation (KDC). Results offer evidence-based foundations that a strong correlation exists between centrality of streets, especially betweenness centrality, and the location of shops and services at the neighbourhood scale. This issue is at the heart of the current debate in urban planning and design towards the making of more sustainable urban communities for the future. Our results also support the "predictive" capability of the MCA model as a tool for sustainable urban design.
19 citations
TL;DR: In this paper, the effect of motion on disease spreading in a system of random walkers which additionally perform long-distance jumps was studied, showing that a small percentage of jumps in the agent motion is sufficient to destroy the local correlations and to produce a large drop in the epidemic threshold, well explained in terms of a mean-field approximation.
Abstract: We study the effect of motion on disease spreading in a system of random walkers which additionally perform long-distance jumps. A small percentage of jumps in the agent motion is sufficient to destroy the local correlations and to produce a large drop in the epidemic threshold, well explained in terms of a mean-field approximation. This effect is similar to the crossover found in static small-world networks, and can be furthermore linked to the structural properties of the dynamical network of agent interactions.
10 citations
Posted Content•
TL;DR: It is shown that models of epidemic spreading in complex networks can be applied to the problem of tuning and controlling the dissemination of information in wireless ad hoc networks composed of devices carried by individuals, i.e., human-based networks.
Abstract: Epidemics-inspired techniques have received huge attention in recent years from the distributed systems and networking communities. These algorithms and protocols rely on probabilistic message replication and redundancy to ensure reliable communication. Moreover, they have been successfully exploited to support group communication in distributed systems, broadcasting, multicasting and information dissemination in fixed and mobile networks. However, in most of the existing work, the probability of infection is determined heuristically, without relying on any analytical model. This often leads to unnecessarily high transmission overheads.
In this paper we show that models of epidemic spreading in complex networks can be applied to the problem of tuning and controlling the dissemination of information in wireless ad hoc networks composed of devices carried by individuals, i.e., human-based networks. The novelty of our idea resides in the evaluation and exploitation of the structure of the underlying human network for the automatic tuning of the dissemination process in order to improve the protocol performance. We evaluate the results using synthetic mobility models and real human contacts traces.
07 Dec 2007
TL;DR: In this article, a modified version of dynamical clustering based on chaotic Rossler oscillators is presented, which is tested on real and computer generated networks with a well known modular structure.
Abstract: A new dynamical clustering algorithm for the identification of modules in complex networks has been recently introduced [1]. In this paper we present a modified version of this algorithm based on a system of chaotic Rossler oscillators and we test its sensitivity on real and computer generated networks with a well known modular structure.
TL;DR: A modified version of this dynamical clustering algorithm for the identification of modules in complex networks based on a system of chaotic Rossler oscillators is presented and its sensitivity is tested on real and computer generated networks with well known modular structure.
Abstract: A new dynamical clustering algorithm for the identification of modules in complex networks has been recently introduced \cite{BILPR}. In this paper we present a modified version of this algorithm based on a system of chaotic Roessler oscillators and we test its sensitivity on real and computer generated networks with a well known modular structure.
07 Dec 2007
TL;DR: In this article, the authors show that Probability Density Functions (PDFs) for the avalanche size differences at different times have fat tails with a q-Gaussian shape.
Abstract: We discuss recent results on a new analysis regarding models showing Self‐Organized Criticality (SOC), and in particular on the OFC one. We show that Probability Density Functions (PDFs) for the avalanche size differences at different times have fat tails with a q‐Gaussian shape. This behavior does not depend on the time interval adopted and it is also found when considering energy differences between real earthquakes.
01 Oct 2007
TL;DR: The analysis indicates that mediators differ in the relevance: cytokines involved in innate immunity and inflammation and some hormones rank highest in the network, revealing that the most prominent mediators of the immune system (IS) are molecules involved in ancestral types of defence mechanisms highly integrated with the adaptive IS.
Abstract: Immune cell type communicates with other cell types through mediators (cytokines, chemokines, hormones). A quantitative analysis of the topological properties of such an immune network is still lacking. We present a method for quantifying the relevance of mediators in the human immune network, based on the concept of efficient communication. The analysis indicates that mediators differ in the relevance: cytokines involved in innate immunity and inflammation and some hormones rank highest in the network, revealing that the most prominent mediators of the immune system (IS) are molecules involved in ancestral types of defence mechanisms highly integrated with the adaptive IS.
[ DOI : 10.1685/CSC06145] About DOI